Title

Identifier

Author

Degree

Master of Science in Civil Engineering (MSCE)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

The behavior of unsaturated soils is different from the behavior of saturated soil deposits. Unsaturated soils have more than two phases; the pore water pressure in unsaturated soils is negative. The behavior of unsaturated soil when a dynamic loading such as an earthquake loading is imposed on them, the susceptibility of lab tested soils to liquefaction is investigated in this study. As the phenomenon of liquefaction occurs only in the case of saturated soil deposits, the behavior of unsaturated soil under these conditions is investigated. Sand and silty sand are used in this study, wetting and drying soil water characteristic curves are plotted from the data obtained using Buchner funnel setup, samples are tested at several drying cycles. It is observed that the drier the soil the more resistant it is to liquefaction, which is in agreement that saturated soil deposits are prone to liquefaction while unsaturated soil deposits may settle. Shear wave velocity parameter obtained from the bender element test setup is used to assess the liquefaction potential of soil deposits. It is observed that with increase in water content shear wave velocity and stiffness decrease. Ground response analysis is performed using Edushake package, and several plots of ground motion, object motion, shear stress, shear strain etc.., are plotted by using the properties of the soil tested in the laboratory and simulating an input motion. Yerba earthquake is chosen for simulation in this study as it involved damage to unsaturated soils during the motion. It is found that considering the peak acceleration, velocity and displacement the combination of sand and silty sand has higher frequency when subjected to same input motion than the problem with sand deposits which is in agreement that when sand deposits have seams of silt their susceptibility to liquefaction increases